Neil S. Mandel

ASYMMETRIC ACYLATION REACTIONS OF CHIRAL IMIDE ENOLATES. THE FIRST DIRECT APPROACH TO THE CONSTRUCTION OF CHIRAL β-DICARBONYL SYNTHONS

Acylation de 2 propionimides chirales: isopropyl-4 propionyl-3 oxazolidone-2 et methyl-4 phenyl-5 propionyl-3 oxazolidone-2

Urinary Tract Stone Disease in the United States Veteran Population. II. Geographical Analysis of Variations in Composition

The geographical distribution of crystalline components observed in urinary tract stones in the continental United States has been studied in the United States veteran population. Since the veteran population is at risk for urolithiasis the National Veterans Administration Crystal Identification Center was established in 1983 for the characterization of all crystal-containing veteran patient samples using high resolution x-ray powder diffraction. The geographical distribution of whewellite, weddelite, apatite, brushite, struvite, uric acid and uric acid dihydrate is presented. The percentage occurrence of the crystalline components, percentage occurrence of admixed stones and geographical distribution of the number of components in admixed stones also are presented. The data highlight that although the southeastern United States has the highest patient discharge rate for stones, this high discharge rate appears to be correlated specifically with a high discharge rate for calcium oxalate stones and not with a high discharge rate for any of the other common stone components.

Study of a rat model for calcium oxalate crystal formation without severe renal damage in selected conditions

Abstract  Background:  Although nephrotoxic in high doses, ethylene glycol (EG) has been used with ammonium chloride (NH4Cl) or vitamin D3 to study calcium oxalate stone formation in rat models. In the present study we used EG alone or with NH4Cl to study hyperoxaluria, crystaluria, and crystal attachment to renal epithelial cells in rats with minimal renal damage.

Calcium oxalate-crystal membrane interactions: dependence on membrane lipid composition.

PURPOSE Urolithiasis is clearly a multifaceted process, progressing from urine supersaturation to the formation of mature renal calculi. Retention of microcrystals by the urothelium is a critical event in stone maturation. Membrane phospholipids appear to be involved in the attachment of stone crystals to kidney epithelium. MATERIALS AND METHODS The current study quantitates crystal-membrane interactions following selective changes in the red blood cell (RBC) membrane phospholipid composition by using a crystal-induced membranolytic assay. RESULTS Membrane enrichment with anionic phospholipids was found to greatly increase crystal-membrane interactions. Crystal-membrane interaction was associated with an increase in the negative charge on the RBC membrane surface. CONCLUSIONS Specific membrane compositions seem to facilitate the formation of crystal attachment region on the RBC surface that is necessary for effective crystal attachment to the cell membrane.

Crystal-Cell Interactions: Crystal Binding to Rat Renal Papillary Tip Collecting Duct Cells in Culture

Retention of stone crystallites by urothelium is clearly one of the prime requisites for urinary stone disease. Studies in the literature as early as 1937 have highlighted that the initiation of renal calculi followed the formation of subepithelial calcified plaques in the renal pelvis. The renal papilla is one of the primary sites for crystal fixation and stone maturation. We have developed an in vitro model system for the study of kidney stone crystal retention to tubular epithelium using rat renal papillary collecting tubule (RPCT) cells in primary culture. We have qualitatively and quantitatively analyzed the binding of preformed calcium oxalate monohydrate (COM), hydroxyapatite (HA), and uric acid (UA) crystals to RPCT cells. Our goal was to determine if three common urinary stone crystals evidenced different crystal-cell binding characteristics. Also, since these crystals are frequently observed admixed in stones, we have studied the inhibitive binding characteristics of these crystals with RPCT cells. The RPCT cells in culture grow both as the typical polygonal cells in monolayer and as clumps of aggregated cells. The cells in the aggregates are viable epithelial cells that have lost their attachment to the basement membrane, resulting in the exposure of surface molecules that would not normally be present unless the cells were damaged or if there was a loss of intercellular tight junctions. COM, HA, and UA crystals all preferentially bound to the aggregated cells and all exhibited similar saturable binding patterns.(ABSTRACT TRUNCATED AT 250 WORDS)

Membrane Interactions with Calcium Oxalate Crystals: Variation in Hemolytic Potentials with Crystal Morphology

Crystal-induced membranolysis of human red blood cells has been quantitated for calcium oxalate monohydrate and calcium oxalate dihydrate crystals. Calcium oxalate monohydrate crystals are significantly more membranolytic than calcium oxalate dihydrate crystals at constant surface area. If the crystal morphology of calcium oxalate monohydrate is altered by grinding, the lytic potential at constant surface area is markedly reduced. However, altered calcium oxalate dihydrate crystals are as lytic as natural calcium oxalate dihydrate crystals at constant surface area. Differences in the calcium oxalate monohydrate and dihydrate crystal structures, specifically the structural characteristics of the disordered water channel in calcium oxalate dihydrate, can explain these different membranolytic characteristics.

Urinary tract stone disease in the United States veteran population. I. Geographical frequency of occurrence.

The geographical distribution of hospitalization for urinary tract stone disease in the continental United States has been studied in the United States veteran population. The current study has been facilitated by the availability of a centralized computer data base containing the International Classification of Disease Codes for all hospital discharges at all Veterans Administration medical facilities. These data have allowed for an accurate mapping of the hospital discharge rate for urinary tract stone disease (stone discharge rate) in a population at risk for urolithiasis. Stone discharge rate data have been compared to those from the 2 previous studies conducted in general hospitals in 1952 and 1974. The stone discharge rate was 7.9 +/- 3.4 in 1952, 9.97 +/- 2.82 in 1974 and 7.58 +/- 2.01 in our study. These data indicate that the urinary tract stone discharge rate has not markedly varied during the last 34 years and also that the southeastern states still evidence the highest hospital discharge rate for urinary tract stone disease.

A Drosophila Model Identifies a Critical Role for Zinc in Mineralization for Kidney Stone Disease

Ectopic calcification is a driving force for a variety of diseases, including kidney stones and atherosclerosis, but initiating factors remain largely unknown. Given its importance in seemingly divergent disease processes, identifying fundamental principal actors for ectopic calcification may have broad translational significance. Here we establish a Drosophila melanogaster model for ectopic calcification by inhibiting xanthine dehydrogenase whose deficiency leads to kidney stones in humans and dogs. Micro X-ray absorption near edge spectroscopy (μXANES) synchrotron analyses revealed high enrichment of zinc in the Drosophila equivalent of kidney stones, which was also observed in human kidney stones and Randall’s plaques (early calcifications seen in human kidneys thought to be the precursor for renal stones). To further test the role of zinc in driving mineralization, we inhibited zinc transporter genes in the ZnT family and observed suppression of Drosophila stone formation. Taken together, genetic, dietary, and pharmacologic interventions to lower zinc confirm a critical role for zinc in driving the process of heterogeneous nucleation that eventually leads to stone formation. Our findings open a novel perspective on the etiology of urinary stones and related diseases, which may lead to the identification of new preventive and therapeutic approaches.

Regulation of pH in rat papillary tubule cells in primary culture.

To investigate the mechanisms responsible for urinary acidification in the terminal nephron, primary cultures of cells isolated from the renal papilla were grown as monolayers in a defined medium. Morphologically, cultured cells were epithelial in type, and similar to collecting duct principal cells. Cell pH measured fluorometrically in monolayers grown on glass slides showed recovery from acid loads in Na+-free media. Recovery was inhibited by cyanide, oligomycin A, and N-ethylmaleimide. Cyanide and oligomycin inhibited recovery less in the presence than in the absence of glucose. When cells were first acid loaded in a Na+-free medium and then exposed to external Na+, pH recovery also took place. This recovery exhibited first-order dependence on Na+ concentration and was inhibited by 5-(N-ethyl-N-isopropyl)amiloride. These studies demonstrate that in culture, collecting duct principal cells possess at least two mechanisms for acid extrusion: a proton ATP-ase and an Na+-H+ exchanger. The former may be responsible for some component of the urinary acidification observed in the papillary collecting duct in vivo; the role of the latter in acid-base transport remains uncertain.

CALCIUM OXALATE CRYSTAL ATTACHMENT TO CULTURED KIDNEY EPITHELIAL CELL LINES

PURPOSE Cultured kidney epithelial cell lines have frequently been used in urolithiasis research, and in particular in studies related to the interactions between stone crystals and cell membranes. There is evidence that when epithelial cell lines are transformed or serially passed to immortalize them, they experience changes in both cell physiology and morphology. Stone research utilizing cell cultures is frequently necessary due to the lack of an animal model for spontaneous stone disease. However, the interpretation of these cell culture research studies might be clouded by any significant differences in cell physiology between primary cells and continuous cell cultures. Therefore, the present study was conducted to compare calcium oxalate monohydrate (COM) crystal attachment to two primary kidney epithelial cell lines and to various continuous cell lines. MATERIALS AND METHODS The cell lines surveyed were primary mouse proximal tubule cells (pMPT), primary inner medullary collecting duct cells (pIMCD), semi-continuous inner medullary collecting duct cells (cIMCD), BSC-1 cells, COS-1 cells, LLC-PK1 cells, MDCK cells, NRK-52E cells, and OK cells. All cell lines were cultured under identical conditions and the amount of COM attachment was measured using radioactive labeled COM crystals. RESULTS COM crystal interaction with continuous kidney epithelial cells varied by a factor of two among the different cell lines. In general, cells that grew as regular, confluent cell monolayers, such as pMPT, pIMCD and cIMCD cells, exhibited the lowest levels of crystal attachment. Neither changes in membrane fluidity nor loss of normal epithelial cell membrane asymmetry seemed to correlate well with crystal attachment. After nine days of continuous cell culture, COM attachment to cIMCD cells dropped by 61 percent while crystal attachment to MDCK cells remained unchanged. It is unclear what makes these cell lines more resistant to crystal attachment compared to continuous cell lines. CONCLUSIONS The significant difference in COM attachment between primary kidney epithelial cells and continuous epithelial cell cultures and the apparent differences in growth morphology between primary and continuous cell cultures must be considered when selecting a cell line for use in kidney stone research. Comparison of cIMCD cells and MDCK cells during extended culture time revealed one possible explanation for the differences in COM attachment: the formation of a mature, end-differentiated, non-dividing cell monolayer could protect the cells from crystal attachment.